Switch control device



May E, DQE'LER ET AL swmc'ii' CONTROL DEVICE filed July 5', 19:55

Patented May 11, 1937 UNITED STATES SWITCH CONTROL DEVICE Erich Dobler and Ludwig Holm, Stuttgart, Germany, assignors to Robert Bosch Aktiengesellschaft, Stuttgart, Germany Application July 1935, Serial No. 80,004 In Germany July 27, 1934 8 Claims.

The present invention relates to a controlling device, which is adapted more especially for the controlling of' refrigerating plants. 7

It is known in controlling devices to use a 5 snap-spring having two stable end-positions for the sudden effecting of switch movements. This snap-spring is struck by the member dependent on whose position the switching operation is to be carried out, and flies over from its one end- 10 position into the other end-position, and thereby switches any circuit on or oil. It has been suggested to provide an elastic connecting piece arranged between the snap-spring and the controlling member dependent on whose position a switching operation is to be eflected. By this means a controlv operation does not take place at each of the smallest movements of the controlling member.

In the controlling devices of this kind hitherto known the controlling member consists of a rocking lever, to the side of which facing the bottom of the switch casing the elastic connecting piece in the form of leaf-springs is fastened with sidefaces directed at right angles to the casing bottom. In this, construction, these two controlling members take up a comparatively large amount of room. as they lie above each other, and also above the snap-spring operated by them, they involve a relatively high switch 30 casing. Further, the controlling lever must have a broad surface parallel to the switch bottom, so that it may afford sufficient room for fastening the holding bolt of the leaf-spring.

The construction is substantially simplified and 5 made more compact according to the invention wherein the controlling lever takes the form of a metal strip which is narrow in the rocking direction, to the side faces of which are fastened the leaf -springs which bear with their broad faces 40 on the snap spring.

An example of construction according to the invention is shown in the drawing, in which:-

Figure 1 is a plan view, with the upper switch cover removed. 7

Figure 2 is a section on the line 2-2 of Fig. 1. Figure 3 a section on the line 3-4 of'Figure 1, and

Figure 4 is a detailed view, looking to the right of Figure 1, of the switch resetting mechanism.

It is a thermostat, which responds to the temperature of the refrigerating chamber of a refrigerating plant. It consist's'of a bellows II,

which is filled with a liquid the volume of which varies greatly on a change of temperature, and

55 is loaded by a spring l2, the compression of which can be varied by a screw 38 when an operating knob I2 is turned. The interior of the bellows II is connected by a pipe H with a temperaturesensitive element (not shown), arranged in the chamber whose temperature is to be controlled. The resiliently loaded bellows II and the spring l2, together with the operating knob II, are mounted on a plate It, which is inserted in the lower part It of a switch casing and is connected thereto by screws.

Th movements of the bellows ll produced by alterations in temperature are transmitted by means of a spindle It to a lever 2B, of metallic strip form, and pivoted on a pin is, two leafsprings 2| being laterally riveted to said lever. The leaf-springs 2i engage a snap spring 22, the ends of which are mounted in bearing pins 22, which are also fastened on the plate It. The snap-spring 22 carries a contact 24, the countercontact 25 of which is resiliently seated on a carrier member 26 secured to the plate It. The lever is not rigidly connected to the spindle it of the thermostat III, on the contrary it bears loosely against a pin 21 carried through the spindle it, and is pressed against said pin by the bent up straight end of a helical spring 28. Such a resilient coupling has the advantage that no great frictional forces occur on the movement of the thermostat bellows. The helical spring 20 is fitted on a bolt 29, which, like the other part of the switch, is secured to the plate It. To the switch plate It is also connected a support 20 for a bimetallic strip 3| which serves as an excess current safety device. One free end of a lever 33 engages in a hole 22 in the bimetallic strip, and the other end of the lever bears on the lever 20 which operates the snap-spring 22 of the switch. 34 is a wire coil which heats the bimetallic strip when an excess current'occurs. is a starting switch, which, together with the remaining parts of the switch, can be arranged in the casing It.

The manner of operation is as follows:-- When the parts are in the position shown in Figure 1 the contacts are closed. If now the temperature in the refrigerating chamber sinks, then the volume of the liquid therein becomes smaller and the spring l2 compresses the bellows l l Consequently, the spindle I8 is moved to the left whereby the lever 20 is rocked to the left, so that one of the leaf-springs 2| presses against the snap-spring 22, which now flies over from, one end-position into the other end-position, and thereby separates the contacts 2|, 25. If the current is to be switched off, the switch knob is correspondingly turned, by which one end of the lever If snaps out of the opening 82, and the other end of the lever If is pressed by means of a spring it against the lever 20, which brings the snap-spring 2! into the other position for flying over, whereby the contacts 24, II are released. When an excess current occurs, the resistance wire it heats the bimetallic strip II, which bends owing to heating, whereupon one end of the lever 33 springs out of the hole 32 and the other end is pressed by means of the force of the spring 38 against the lever 10, which causes the snap spring 22 to fly over so that the current is switched off. The switch can be reset by turning knob If counterclockwise, at which time the beveled end of a lever 40 pivotally mounted on disk II will engage the lever 33 and move it upward to reset the switch. A spring I normally holds lever 40 against a pin 42, the spring yielding to permit said lever to swing on its pivot without actuating lever II when the knob ll and disk I! are turned clockwise.

The leaf-springs II are preferably regularly tapered from the place where they are riveted towards the free end which is in engagement with the snap-spring, so that on the displacement of a rider 31 the curve of the leaf-springs is altered so as to regularly rise or fall. By this means the switch device can be adjusted so as to be very sensitive when fixing up the apparatus.

It is further preferable to make the adjustable rider I1 in U-shape with an eye-shaped web. By this means the rider can be easily gripped to move it, yet nevertheless in any position presses the leaf-springs 2| resiliently on the flat faces of the lever 20. In connection with the lateral arrangement of the leaf-springs II, this form of rider has also the advantage that the rider is held by its own springiness alone on the leaf-springs II and the lever 20.

We declare that what we claim is:

l. A switch control device for apparatus such as refrigerators, comprising a thermostat, a rocking lever of metallic strip form angularly displaceable by said thermostat according to temperature variations, and with the faces of said lever extending laterally of its direction of movement, a pair of leaf springs, the flat faces of which are secured to the flat faces of one end of said rocking lever, a snap spring having a flat face extending between and having a direct fiat face to face contact with said leaf springs and which is stable in two end positions of displacement, and switch contacts, one of which is carried by said snap spring.

2. A switch control device for apparatus such as refrigerators, comprising a thermostat, a rocking lever of metallic strip form angularly displaceable by said thermostat according to temperature variations with the faces of said lever extending laterally of its direction of movement, a pair of tapered leaf springs the flat faces of which are secured to the flat faces of one end of said rocking lever, and the cross-section of each of which is gradually reduced towards the free end thereof, a snap spring having a flat face extending between and having a direct flat face to face contact with said leaf springs, and which is stable in two end positions of displacement, and switch contacts, one of which is carried by said snap spring.

3. A switch control device for apparatus such as refrigerators. comprising a thermostat, a rocking lever of metallic strip form, angularly displaceable by said thermostat upon a temperature variation with the faces of said lever extending laterally of its direction of movement, a pair of tapered leaf springs the hat faces of which are secured to the flat faces of one end of said rocking lever, a displaeeabie rider resiliently embracing said leaf springs and said lever intermediate their ends, a snap spring having a flat face extending between and having a direct lat face to face contact with said leaf springs and which is stable in two end positions of displacement, and switch contacts one of which is carried by said snap spring.

4. A switch control device for apparatus such as refrigerators, comprising a thermostat, a rocking lever of metallic strip form, angularly displaceable by said thermostat upon a temperature variation, a pair of tapered leaf sprints the flat faces of which are secured to the flat faces of one end of said rocking lever, a displaceable rider consisting of a U-shaped yoke and an eye-shaped web, resiliently embracing said leaf springs and said lever intermediate their ends. a snap spring havingafacetofacecontactwithsaidleaf springsandwhichisatableintwoendpodtions ofdispiacementandswitchcontactsonaof which is carried by said snap spring.

5.Aswifehcontroldeviceforapparatusmeh as refrigerators, comprising a thermostat. an elementadaptedtobeoperatedbysaidthermoatat according to temperature variations, resilient meansoneendofwhichisaeousedtosaidelement,asnapspringadaptedtobemappadover fromonepositiontoanotherandviceversaby theotherendofsaidreaiiientmeanaandmeans for regulating the strength of said resilient means, the cross-section of said resilient means gradually decreasing frun its secured end to the other end, such regulating means being movable on said resilient means to regulate the effective length and cross-section thereof.

a. A switch control device for apparatus such as refrigerators, comprising a thermostat, a lever angularly dispiaceabie by said thermostat according to temperature variations, resilient means oneendofwhichissecin'edtoaaidlevenasnap springactuatedbytheotherendofsaidresilient means and arranged to snap from one position to the other and vice veraa for quickly making or breaking an electric circuit. and a displaceable rider embracing said rollient means and varying,whendisplaoed.thereailientstrengthof -id resilient means. the cross-section of said reailiqst means gradually decreasing from its secured end effective length and cross-section thereof.

7. A switch control device for apparatus such as refrigu-ators, comprising a thermostat. a lever angulariy displaceable by cording to temperature variations. two leaf springs at opposite faces of said lever. one ofeachleafspringbeingsecuredtosaidlever. a snap spring in adJacent connection and actuated by the other ends of said leaf springs and arrangedtobesnapped fromonepoaitionto the other and vice versa for quickly closing or breaking an electric contact, a displaceable rider embracing said leaf springs to adjust the resilient strength of the leaf springs, the cross-section of said leaf springs diminishing from their secured ends to their other ends to reduce the stiifnas of said leaf springs toward said other ends, displacement of said rider relative to said leaf Qrlngs varying the effective length and cross-section thereof. 1

8. A switch control device for apparatus such as refrigerators, comprising a thermostat, an element adapted to be operated by said thermostat 7 according to temperature variations, a snap spring adapted to be snapped over from one position to another and vice versa, resilient means for transierring the movement or said element to said snap spring, the two ends of said resilient means being connected with said element and said snap 0 spring, the one end being connected solidly and the other loosely, the cross-section of the resilient 1 means gradually decreasing from its secured end to the other end, and means ior'reguiating'the strength of said resilient means, such regulating means being movable on said resilient means to regulate the eilective length and cross-section thereof.

ERICH DOBLER.

LUDW'IG HOLM. 

